The insertion of the term "indigenous peoples" in the Mexican Constitution in 2001 launched an epistemological, conceptual, cultural, and social debate which revealed the lack of theoretical and conceptual definition of terms such as culture, identity, indigenous people, or ethnicity. At the same time, every day uses have turned the meaning of these concepts vaguer. For their part, social sciences have made of the issue one of their own and carried out a number of works which none the less constitute but sporadic efforts leading to no consensus. As a result, the meaning of these concepts still varies from one field to another, from the legal and cultural to the social and financial. It is thus urgent to provide these concepts witin a minimum of clarity in order to offer new premises which would bring theory and social reality closer, having in mind a society that can be equal and different at the same time.